Sensor devices and methods for determining the position of metal bodies are known from the prior art. Eddy-current sensors have a coil to which a high-frequency alternating current is fed, as a result of which an alternating electromagnetic field is formed around the coil. The field lines of the high-frequency alternating field emerge in this case from the sensor plane. If an electrically conductive object, in particular a metal body, approaches the eddy-current sensor, the alternating field induces eddy currents in the metal body. Said eddy currents themselves form their own electromagnetic field which counteracts the coil field as a result of which the impedance or inductance of the coil changes. In this case, the impedance of the coil changes in proportion with the distance of the metal body from the coil, with the result that the distance or a change in distance of the metal body from the coil can be determined on the basis of the impedance or change in impedance. In order to feed or operate the coil with high-frequency alternating current and in order to detect an impedance or change in impedance of the coil, the eddy-current sensor generally has a corresponding device which may be formed from one or more electrical/electronic components.
These days, it is sought to configure corresponding eddy-current sensors or sensor devices to be as small as possible in order to save installation space, in particular in the motor vehicle. As a result of this, correspondingly small conductor-track geometries are necessary for such eddy-current sensors. However, these have a low inductance. The resonant circuits resulting from this must therefore be operated with high frequencies of up to 100 MHz. In order to be able to evaluate this frequency with frequency counters, the evaluation device must likewise operate at a correspondingly high frequency. Evaluation devices or calculation units which are conventionally used in the automotive industry are not able to directly work with such high frequencies. For this purpose, so-called high-end evaluation devices are necessary, which disagreeably affect manufacturing costs, however.